In the field of substance abuse treatment, "continuity of care" refers to the receipt of multiple levels of care or treatment modalities, which range from inpatient or residential to outpatient and ongoing monitoring (McKay, 2009). Implicit in the continuity of care framework is the existence of interorganizational relationships among treatment providers. References to "systems of care" in the substance abuse treatment literature assume such "systems" are well-coordinated. Descriptions of the treatment system, however, suggest the opposite. Treatment systems are fragmented, with little coordination across modalities (McLellan et al., 2005;Saitz et al., 2008). At the point of discharge from detox, patients are at high risk of relapse and, therefore, vulnerable to system failures. To improve systems of care for vulnerable populations, we need to first examine their structure and effectiveness (Morrissey, Johnsen, &Calloway, 1996). The proposed research and training program includes skills development in data management, network analysis, and multi-level analysis. The proposed study is among the first to study substance abuse treatment systems from an interorganizational network perspective. The study proposed in this application is a cross-sectional, analytical study of the relationship between interorganizational networks in county substance abuse treatment systems and readmissions to detox. Social network analysis will be used to measure connectedness among service providers. The network data are patient transfers from one provider to another provider within 14 days of discharge. Social network analysis is an innovative research strategy that can provide important insights into services coordination in substance abuse treatment systems of care. The relevance of social network analysis to the health services field is evidenced by the recent NIH Program Announcement on Social Networks and Health (PAR-10-146). Because of the high cost of detox services and health risks associated with continued substance abuse, readmission to detox is an important performance measure for substance abuse treatment systems (McLellan et al., 2005). The study focuses on 47 counties in California that reported detox admission data to the state in 2008-2009. Observing the pathways of patients from series of admissions and discharges to and from treatment providers enables assessing connections among providers. The study uses multi-level analysis to predict patient readmission to detox (N=24,713). The project will analyze data from two from administrative databases: treatment episode data from the California Outcomes Measurement System (CalOMS), and facility-level data from the National Survey of Substance Abuse Treatment Services (N- SSATS). Interorganizational networks have enjoyed very little attention in the addiction health services research field. The proposed research fills this gap and brings a broader ecological perspective to the substance abuse treatment field. PUBLIC HEALTH RELEVANCE: The proposed research and training program is among the first to study substance abuse treatment systems from an interorganizational network perspective. The study proposed in this application is a cross-sectional, analytical study of the relationship between interorganizational networks in county substance abuse treatment systems and readmissions to detox. Archival data from the California Outcome Measurement System (CalOMS) will be used to map linkages among substance abuse treatment providers and measure services integration within provider networks.